This invention is an improvement over the method and apparatus for color grading disclosed in the copending U.S. Pat. No. 3,998,555, issued on Dec. 21, 1976, and entitled: Color Grading Apparatus. As discussed in this copending application, there has been utilized, especially in commercial food processing, apparatus for measuring accurately reflected light in various wavelength regions to determine various properties of products.
Such apparatus has been especially useful in the controlling of continuous processing machinery such as equipment for blanching or roasting of peanuts, french-fried potatoes, or for peeling potatoes, et cetera. In such controlled processes, the color of the product is detected as it leaves the processing area. The color changes as the degree of processing is altered and the resultant signal responsive to the color is used to control the processing variables. In this manner the process is controlled continuously for the regulation of the heat to gain a desired degree of cooking or for regulating the degree of peeling a product by altering the speed at which the product is fed through the processor, or for regulating other variables in such equipment.
To eliminate the effects of the reflected light changing in intensity due to such variables as changes in the product volume, distance from the photosensors to the products, et cetera, the reflected light is usually measured in two ranges with the resultant signals compared to generate a ratio signal. By generating such a ratio signal, the variations in the signals resulting from variables not being controlled are canceled out. In the past the light regions measured have usually been centered around 5430 A in the green region and around 6400 A in the red region. By using these wavelength regions, light sources and components are somewhat readily available.
However the degree of change in the ratio in the wavelength regions between the properly processed and improperly processed product is frequently only about 3%. Thus the electronic apparatus used to detect the change in the ratio is required to be quite precise in measuring the changes in light intensities. However the environment in which such equipment operates frequently is of a higher or at least a frequently changing temperature, can be of a high humidity and can involve certain other characteristics such as a poluted atmosphere attendant to the heating, steaming, cooking or processing of food products. Thus it is very difficult to maintain the equipment at the operating precision necessary for measuring such small amounts of change in the light reflectance.
It is the purpose of this invention to provide an improved color grading apparatus capable of effecting a greater amount of change in the signal ratio generated in two light regions for measuring the processing of the product and thereby rendering a more accurate determination of the degree and effectiveness of such processing. Also this invention provides for a more reliable and stable detection of the color ratio by the provision of a unique light source for the infrared light region.